1. Field of the Invention
This invention pertains to processes for recovering oil from underground reservoirs that have rock characteristics such that recovery does not proceed readily by flowing to a well bore.
2. Description of the Prior Art
Recovery of oil from an underground reservoir sometimes does not proceed readily by flow into a well bore penetrating the reservoir because the reservoir rock lacks permeability or the oil lacks gas in solution or because the reservoir rock is fractured, such as the Spraberry sand of West Texas and the Austin Chalk, Buda lime of Central Texas. Recovery of the oil in place in such rocks is notoriously small (5%) and the amount of residual oil unrecoverable by presently known methods is exceedingly large, in the billions of barrels. Serpentine plugs of Texas have produced but a small fraction of their oil such as Lytton Springs, Thrall, Chapman-Abbot, etc.
Numerous techniques, so called enhanced, secondary and tertiary recovery, have been tried unsuccessfully to recover oil from tight reservoir rocks. They all involve pushing the oil horizontally through the reservoir rock without changing its permeability, at times even with lowering the viscosity of oil. All these processes are inefficient and often they are rank failures.